Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > The Golden Age of Model Rocketry > Model Rocket History
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 09-21-2017, 02:29 AM
Royatl's Avatar
Royatl Royatl is offline
SPEV/Orion wrangler
 
Join Date: Mar 2005
Location: Atlanta, GA
Posts: 2,645
Default 1972 D12-3. Should I fly it?

I'm thinking of flying a junk rocket with a D12-3 made in April 1972 at our club launch this Saturday.

What say you? Should I do it? What do you think will happen if I do?

This D12-3 has been in my possession since it was first purchased at a hobby store. There was a time in the 80's that it spent two or three years in the attic, but since then it has been in a fairly constant normal indoor environment. My theory is that thermal-cycled motors can return to stability over long periods of time.

Attached Thumbnails
Click image for larger version

Name:  IMG_0506.JPG
Views: 49
Size:  1.24 MB  
__________________
Roy
nar12605
Reply With Quote
  #2  
Old 09-21-2017, 08:08 AM
tbzep's Avatar
tbzep tbzep is offline
Dazed and Confused
 
Join Date: Mar 2005
Location: TN
Posts: 11,610
Default

Quote:
Originally Posted by Royatl
I'm thinking of flying a junk rocket with a D12-3 made in April 1972 at our club launch this Saturday.

What say you? Should I do it? What do you think will happen if I do?

This D12-3 has been in my possession since it was first purchased at a hobby store. There was a time in the 80's that it spent two or three years in the attic, but since then it has been in a fairly constant normal indoor environment. My theory is that thermal-cycled motors can return to stability over long periods of time.


If your attic is like mine, that sucker has spent three years cycling from 75 at night up to 150 degrees in the day during the summer and down to the 30's or less in the winter. I'd only fly it if you like seeing roman candles.
__________________
I love sanding.
Reply With Quote
  #3  
Old 09-21-2017, 10:36 AM
hcmbanjo's Avatar
hcmbanjo hcmbanjo is offline
When Pigs Fly!
 
Join Date: Sep 2005
Location: Orlando, FL
Posts: 1,102
Default

I've launched many old 1970 engines with great success.
But, my engines were stored indoors in an air conditioned closet.
The best answer to the old D12 is "I'm thinking of flying a junk rocket."
__________________
Hans "Chris" Michielssen
Old/New NAR # 19086 SR

www.oddlrockets.com
www.modelrocketbuilding.blogspot.com
http://www.nar.org/educational-reso...ing-techniques/
Your results may vary
"Nose cones roll, be careful with that."
Every spaceman needs a ray gun.
Look out - I'm the Meister Shyster!
Reply With Quote
  #4  
Old 09-21-2017, 10:39 AM
astronwolf's Avatar
astronwolf astronwolf is offline
Lost his Drifter
 
Join Date: Mar 2013
Location: Northeast Ohio
Posts: 1,277
Default

Quote:
Originally Posted by Royatl
My theory is that thermal-cycled motors can return to stability over long periods of time.

Then you need to design an experiment to test that hypothesis. I say fly it. My prediction, based on absolutely no data, is that it will not cato.
__________________
-Wolfram v. Kiparski
NAR 28643 - TRA 15520
MTMA Section #606 President
Reply With Quote
  #5  
Old 09-21-2017, 12:10 PM
rocketguy101's Avatar
rocketguy101 rocketguy101 is offline
frustrated aero
 
Join Date: Sep 2006
Location: Duncan, OK
Posts: 832
Default

I thought the issue with thermal cycling was the differential diametrical change between the case and the propellant slug (due to different coefficient of thermal expansion of the materials) which allowed the propellant to de-bond from the paper case. During the burn, when it reached the OD of the slug there is a sudden large increase in surface area, causing a pressure spike which leads to CATO.

I don't see how this could self heal...but I've wondered if you could put an epoxy fillet at the back of the motor to keep the slug in, like the old EnerJet motors???
__________________
David Stribling
NAR 18402 SR
But it is rocket science!
Get yer Barrowmans here
Reply With Quote
  #6  
Old 09-21-2017, 12:27 PM
Scott6060842 Scott6060842 is offline
Master Modeler
 
Join Date: Sep 2010
Location: NW Pennsylvania
Posts: 665
Default

I would definitely fly it, in something you are not very fond of. Got an old "The Dude" laying around?
Reply With Quote
  #7  
Old 09-21-2017, 01:13 PM
ghrocketman's Avatar
ghrocketman ghrocketman is offline
President, MAYHEM AGITATORS, Inc.
 
Join Date: Jul 2005
Location: Nunya Bizznuss, Michigan
Posts: 13,443
Default

Tape a LONG stick to the motor "Bottle Rocket"-style and launch it from a tube.
Worst that happens is a cato that destroys nothing but the engine casing.
__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL
, if you have to ask what is "NORMAL" , you probably aren't !

Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !
Reply With Quote
  #8  
Old 09-21-2017, 03:17 PM
Doug Sams's Avatar
Doug Sams Doug Sams is offline
Old Far...er...Rocketeer
 
Join Date: Mar 2005
Location: Plano, TX resident since 1998.
Posts: 3,965
Default

Quote:
Originally Posted by rocketguy101
I don't see how this could self heal...
I'm pretty sure it can't I think Roy was just having a little fun with us

Doug

.
__________________
YORF member #11
Reply With Quote
  #9  
Old 09-21-2017, 03:25 PM
LeeR's Avatar
LeeR LeeR is offline
Retired with Way Too Many Kits
 
Join Date: Jun 2007
Location: Colorado
Posts: 3,222
Default

Please fly it, and shoot video. I love a good pyro show.
__________________
Lee Reep
NAR 55948

Projects: Semroc Saturn 1B, Ken Foss Designs Mini Satellite Interceptor
In the Paint Shop: Nothing! Too cold!
Launch-Ready: Farside-X, Maxi Honest John, Super Scamp
Reply With Quote
  #10  
Old 09-21-2017, 04:35 PM
Royatl's Avatar
Royatl Royatl is offline
SPEV/Orion wrangler
 
Join Date: Mar 2005
Location: Atlanta, GA
Posts: 2,645
Default

Quote:
Originally Posted by rocketguy101
I thought the issue with thermal cycling was the differential diametrical change between the case and the propellant slug (due to different coefficient of thermal expansion of the materials) which allowed the propellant to de-bond from the paper case. During the burn, when it reached the OD of the slug there is a sudden large increase in surface area, causing a pressure spike which leads to CATO.

I don't see how this could self heal...but I've wondered if you could put an epoxy fillet at the back of the motor to keep the slug in, like the old EnerJet motors???



No. Understand that the bonding that occurs between the casing and the propellant (and previously pressed nozzle) occurs within seconds under great pressure.
The de-bonding occurs, as you say, from the change in diameters. If fired within a few months after this occurs, you'll get flame propagation through that microscopic separation. My theory is that if the motor now is kept in normal storage conditions, the bonding reoccurs as a function of pressure over time. After all, there is still pressure being applied, as the diameter the casing was made at, is smaller than the chunk of propellant. This might explain why a lot of the early 90's Estes E15's, which were taken from the market due to a high probability of catos, (anecdotally) work perfectly now. The cause of their problems was slightly different. They worked fine when fired within a few months after manufacture, but 'dried out' too much, and started catoing later. But it seems the longer they're just left alone, they "settle in" to their casing.

By the way, I think your idea about the epoxy fillet would just lead to either a nozzle blow out or a split casing.

But it's still just a theory
__________________
Roy
nar12605
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 01:07 PM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe © 1998-2024